The Cohort Follow-up and Database Maintenance core (Core C) serves as the center for data processing, cohort maintenance, cancer documentation, and biospecimen repository for the Health Professionals Follow-up Study, and, thus, it supports each of the projects within this application. The goals of the core are to: (1) develop and mail follow-up questionnaires, (2) process, verify and compile a database of exposure data, (3) document reports of incident cases of cancer, (4) identify and ascertain cause of death among all participants, (5) trace lost subjects and maintain a name and address file, and (6) maintain participation through biennial newsletters and correspondence. The core also serves as a resource to projects which use stored plasma, buffy coat, cheek cells or tumor blocks from cohort members. With input from other investigators on the Program Project, Core C develops and designs the biennial follow-up questionnaire sent to study participants to update information on diet, exposure information, physical activity, and major illnesses. While maintaining continuity with previous questionnaires, new and existing hypotheses are also evaluated and specific wording for questions is scrutinized. Returned questionnaires are checked for completeness, optically scanned, verified for scanning errors, digitally imaged, stored, and a database of exposure information is compiled. Core C uses a variety of methods to trace participants and to maintain high levels of participation. For each two-year follow-up cycle, we average a 94 percent response rate. At present, over 69 percent of participants responded to the 2000 questionnaire after only a single mailing. From the information collected, incident cases of cancer are documented by obtaining medical records. Most deaths are reported through the questionnaire mailings, and searches of the National Death Index are done after each 2-year questionnaire cycle. A major additional component of the study has come through the collection of biological specimens. Efficient procedures have been developed to obtain pathology blocks for prevalent and incident colon polyps, colon cancer, and prostate cancer cases. Core C serves as a resource to projects which use stored specimens.